Android的jackson和httpcliet

最新推荐文章于 2024-05-06 16:59:10 发布

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本文深入探讨了Jackson库在Java中实现JSON与Java对象的互转，以及HttpClient在Android平台上的高效HTTP通信方法。介绍了Jackson的基本用法，包括所需jar包、JavaBean与JSON之间的转换技巧，特别注意包的正确导入。同时，详细解析了HttpClient的使用步骤，包括创建对象、添加参数、设置超时时间、处理响应等关键操作，提供了避免常见错误的解决方案。

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一、jackson

1、Jackson是一个简单基于Java应用库,Jackson可以轻松的将Java对象转换成json对象和xml文档,同样也可以将json、xml转换成Java对象

2、目前只发现JJWT需要使用jackson2.5.zip解压后的3个jar包
jackson-annotations-2.5.0.jar
jackson-core-2.5.0.jar
jackson-databind-2.5.0.jar

3、如果要将JavaBean->json及json->JavaBean则要导入其它的4个jar包
jackson-core-asl-1.9.7.jar
jackson-core-lgpl-1.9.7.jar
jackson-mapper-asl-1.9.7.jar
jackson-mapper-lgpl-1.9.7.jar

注意：不要导错包
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
mport org.codehaus.jackson.map.SerializationConfig;

4、Java->Json
①、ObjectMap
②、JsonGenerator
③、@JsonIgnore
hibernate中一对多、多对多双向关联会出现这种死循环

二、HttpClient

1、HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、
功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和协议。

2、Android已成功集成了HttpClient，这意味这开发人员可以直接在Android应用中使用
HtppClient来提交请求、接收响应

3、HttpClient的使用步骤

①、创建HttpClient对象(想当于创建了一个浏览器对象)
HttpClient httpClient = new DefaultHttpClient();

②、创建HttpGet(或HttpPost)对象
HttpGet HttpGet = new HttpGet("http://www.baidu.com");
HttpPost httpPost = new HttpPost("http://www.baidu.com");

③、添加参数(可选)
setParams(HttpParams params)//HttpGet和HttpPost共有
setEntity(HttpEntity entity)//HttpPost独有

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("age", "20"));
params.add(new BasicNameValuePair("like", "aa"));
params.add(new BasicNameValuePair("like", "bb"));
params.add(new BasicNameValuePair("like", "cc"));
params.add(new BasicNameValuePair("newsCategoryId", "1"));
HttpEntity paramEntity = new UrlEncodedFormEntity(params,"UTF-8");
httpPost.setEntity(paramEntity);

④、发送GET(或POST)请求，并获得响应
HttpResponse httpResponse = httpClient.execute(HttpUriRequest request);

注：

1、HttpUriRequest为HttpGet和HttpPost的父类

2、需要添加允许网络访问权限，不然会报错“java.lang.SecurityException: Permission denied (missing INTERNET permission?)”
<uses-permission android:name="android.permission.INTERNET" />

3、如果地址错误，或服务器未开户，HttpClient这SB会等待N久(>24小时)。
所以请记得设置超时时间，所以请记得设置超时时间，所以请记得设置超时时间

另外HttpClient版本不一样，代码也不一样。下面的4.0版本的写法
httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);// 连接时间
httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 2000);// 数据传输时间

⑤、处理响应

响应状态码(200)
httpResponse.getStatusLine().getStatusCode()

响应头
getAllHeaders()/getHeaders(String name)

响应内容
HttpEntity httpEntity = httpResponse.getEntity();//此对象包含服务器的响应内容
String result = EntityUtils.toString(httpEntity);

4、使用HttpClientUtils与服务器通信

①、Android客户端与服务器通信

②、JSON数据交换
android系统内置了对象json的支持，另外json其实就以下几个对象的使用：
JSONObject、JSONArray、JSONStringer、JSONException

③、web service，底层使用xml交换数据

5、关于org.apache.http.conn.HttpHostConnectException: Connection to refused错误的解决办法

①、增加网络访问权限：

找到 AndroidManifest.xml 文件。在application标签后面加上 <uses-permission android:name="android.permission.INTERNET"/>

②、检查ip地址：

启动的android模拟器吧自己也当成127.0.0.1和localhost，如果使用了localhost或者127.0.0.1则会被拒绝访问，
把ip地址改成实际地址，如：192.168.1.5

三、实例（从java端调数据，增删查改）

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.t212_08">
    
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

HttpClientPost.java

package com.example.t212_08;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.params.CoreConnectionPNames;
import org.apache.http.util.EntityUtils;

import android.os.AsyncTask;

/**
 * 封装 HttpClient对象POST请求
 *
 */
public class HttpClientPost implements Serializable {

	private static final long serialVersionUID = 1777547416049652217L;

	private static HttpClient httpClient = new DefaultHttpClient();

	static {
		httpClient.getParams().setParameter(
				CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);// 连接时间
		httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT,
				3000);// 数据传输时间
	}

	// 字符集
	private static String encoding = "UTF-8";

	// 服务器地址+端口号+项目名
	private static String basePath = "http://192.168.43.130:8080/T212_easyui";

	// 子控制器的路径
	private String path;

	// 保存请求中的参数
	private List<NameValuePair> params = new ArrayList<NameValuePair>();;

	public HttpClientPost(String path) {
		super();
		this.path = path;
	}

	/**
	 * 向POST请求中添加参数
	 *
	 * @param name
	 * @param value
	 */
	public void addParam(String name, String value) {
		if (value == null) {
			params.add(new BasicNameValuePair(name, ""));
		} else {
			params.add(new BasicNameValuePair(name, value));
		}
	}

	/**
	 * 提交POST请求
	 */
	@SuppressWarnings("unchecked")
	public void submit(final HttpClientPost.Callback callback) {
		new AsyncTask() {
			private String json;

			@Override
			protected Object doInBackground(Object... args) {
				try {
					// 1. 创建HttpClient对象

					// 2. 创建HttpGet(或HttpPost)对象
					HttpPost httpPost = new HttpPost(basePath + path);

					// 3. 向POST请求中添加参数(可选)
					if (0 != params.size()) {
						HttpEntity paramEntity = new UrlEncodedFormEntity(
								params, encoding);
						httpPost.setEntity(paramEntity);
					}

					// 4. 发送POST请求，并获得响应
					HttpResponse httpResponse = httpClient.execute(httpPost);

					// 5. 处理响应
					if (200 == httpResponse.getStatusLine().getStatusCode()) {
						HttpEntity responseEntity = httpResponse.getEntity();// 此对象包含服务器的响应内容
						this.json = EntityUtils.toString(responseEntity);
					}
				} catch (Exception e) {
					throw new RuntimeException(e);
				}
				return null;
			}

			protected void onPostExecute(Object result) {
				callback.execute(this.json);
			}

		}.execute();
	}

	public static interface Callback {
		void execute(String json);
	}
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/bt_main_add"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="新增" />

    <Button
        android:id="@+id/bt_main_edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="修改" />

    <Button
        android:id="@+id/bt_main_del"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除" />

    <Button
        android:id="@+id/bt_main_load"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查单个" />

    <Button
        android:id="@+id/bt_main_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查全部" />
</LinearLayout>

MainActivity.java

package com.example.t212_08;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.Map;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button bt_main_add;
    private Button bt_main_edit;
    private Button bt_main_del;
    private Button bt_main_load;
    private Button bt_main_list;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //查找控件
        findViews();

        //绑定监听器
        bt_main_add.setOnClickListener(this);
        bt_main_edit.setOnClickListener(this);
        bt_main_del.setOnClickListener(this);
        bt_main_load.setOnClickListener(this);
        bt_main_list.setOnClickListener(this);

    }

    private void findViews() {
        bt_main_add = (Button) findViewById(R.id.bt_main_add);
        bt_main_edit = (Button) findViewById(R.id.bt_main_edit);
        bt_main_del = (Button) findViewById(R.id.bt_main_del);
        bt_main_load = (Button) findViewById(R.id.bt_main_load);
        bt_main_list = (Button) findViewById(R.id.bt_main_list);
    }


    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_main_add:
                add();
                break;
            case R.id.bt_main_edit:
                edit();
                break;
            case R.id.bt_main_del:
                del();
                break;
            case R.id.bt_main_load:
                load();
                break;
            case R.id.bt_main_list:
                list();
                break;
        }
    }

    private void add() {
        Log.i("test", "add...");
        HttpClientPost post = new HttpClientPost("/jsp/userAction.action");
        post.addParam("methodName","userAdd");
        post.addParam("SerialNo","1");
        post.addParam("uid","001");
        post.addParam("uname","张三");
        post.addParam("upwd","123456");
        post.submit(new HttpClientPost.Callback() {
            @Override
            public void execute(String json) {
                Log.i("server:",json);
            }
        });
    }

    private void edit() {
        Log.i("test", "edit...");
        HttpClientPost post = new HttpClientPost("/jsp/userAction.action");
        post.addParam("methodName","userUpdate");
        post.addParam("SerialNo","1");
        post.addParam("uid","001");
        post.addParam("uname","张三3356");
        post.addParam("upwd","123456");
        post.submit(new HttpClientPost.Callback() {
            @Override
            public void execute(String json) {
                Log.i("server1:",json);
            }
        });
    }

    private void del() {
        Log.i("test", "del...");
        HttpClientPost post = new HttpClientPost("/jsp/userAction.action");
        post.addParam("methodName","userDelete");
        post.addParam("SerialNo","1");
        post.submit(new HttpClientPost.Callback() {
            @Override
            public void execute(String json) {
                Log.i("server2",json);
            }
        });
    }

    private void load() {
        Log.i("test", "load...");
        HttpClientPost post = new HttpClientPost("/jsp/userAction.action");
        post.addParam("methodName","userList");
        post.addParam("uname","张三");
        post.submit(new HttpClientPost.Callback() {
            @Override
            public void execute(String json) {
                Log.i("server3:",json);
                ObjectMapper om = new ObjectMapper();
                try {
                    Map map = om.readValue(json, Map.class);
                    Log.i("server3:",map.get("total").toString());
                    Log.i("server3:",map.get("rows").getClass().getName());
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        });
    }
    private void list() {
        Log.i("test", "list...");
        HttpClientPost post = new HttpClientPost("/jsp/userAction.action");
        post.addParam("methodName","userList");
        post.submit(new HttpClientPost.Callback() {
            @Override
            public void execute(String json) {
                Log.i("server4:",json);
            }
        });
    }
}